Furnace heat exchanger construction



United States Patent O 3 500 814 FURNACE HEAT EXCHANGER CONSTRUCTION Warren H. De Lancey, Elyria, Ohio, assignor to American Standard Inc., New York, N.Y., a corporation of Delaware Filed Apr. 10, 1968, Ser. No. 720,034 Int. Cl. F28f 3/12; F23m 1/02, 9/06 US. Cl. 126-110 8 Claims ABSTRACT OF THE DISCLOSURE THE DRAVINGS FIG. 1 is a sectional view taken through a heat exchanger embodying the invention.

FIG. 2 is a sectional view taken on line 22 in FIG. 1.

FIG. 3 is an enlarged sectional view showing to better advantage a portion of the FIG. 1 structure.

FIG. 4 is a sectional view taken on line 4-4 in FIGS. 2 and 3.

GENERAL ARRANGEMENT In FIG. 1 there is shown a residential hot air furnace 10 having a gun-type oil burner 12 arranged to discharge flames into a combustion chamber means 14. Suitable ports 16 are formed in the side wall of the combustion chamber for directing the hot combustion gases outwardly into the heat exchanger 18. As shown in the drawings the heat exchanger is formed by six metallic plates, number'ed 20 through 25. These plates are stamped to dishlike configurations so that adjacent plates can be pancaked together to form a series of hollow heat transfer fins designated generally by numerals 26, 27 and 28. The peripheral edges of adjacent plates are welded continuously therealong to provide a sealed heat exchanger construction.

As the hot gases pass from the combustion chamber 14 through ports 16 they fan out into the hollow heat transfer. fins 26, 27 and 28. The gases then flow longitudinally within the exchanger as designated generally by the arrows in FIG. 2. As shown in FIG. 1, the heat exchanger connects with a collar or tube 30 which forms a flue for discharge of the gases out of the heat exchanger.

The air to be heated by the exchanger flows along the outer surfaces of the heat exchanger fins 26, 27 and 28. This treated air may flow in the same direction as the combustion gases or countercurrent thereto. In the same or parallel flow arrangement a conventional centrifugal blower 32 may be employed to move the treated air across the exchanger toward a treated air outlet 34.

FURNACE CASING Conventionally furnaces of the illustrated type are positioned either upright for disposition in the basement or a closet, or horizontally (prone) for disposition in an attic or crawl space. The illustrated furnace is adapted for either type of positionment. However for explanation purposes we will assume an upright positionment. The.

3,500,814 Patented Mar. 17, 1970 furnace can then be said to have an upright back wall 36, two upright side walls 38 and 40, a horizontal partition 42 located some distance above the furnace bottom, and a vertical partition 44 spanning the space between side walls 38 and 40. The treated air flows along the outer surfaces of the heat exchanger fins 26, 27 and 28 in the space designated generally by numeral 50. This space is circumscribed by furnace walls 36, 38, 44 and 40. Suitable fiberglass heat insulation 52 may be provided on the furnace wall surfaces.

HEAT EXCHANGER CONSTRUCTION Heat exchanger 18 is preferably hung or suspended from partition 44, as by means of three connecting cylindrical collars 30, 46 and 48, said collars having their opposite end edges welded respectively to partition 44 and heat exchanger plate 20. Collar 30 serves as a flue as previously explained. Collar 46 serves as a sighting duct for enabling the Serviceman to view the interior surfaces of the heat exchanger and the condition of the flame (through the upper port 16). The opening formed by collar 46 is closed by a plate 47 which contains a sight glass 49; plate 47 also mounts a semi-cylindrical baflie 51 which extends into the heat exchanger to deflect upflowing combustion gases toward the hollow fin areas 26, 27 and 28.

The various plates 20 through 25 of the heat exchanger are preferably stamped to identical configurations for cost reasons. Plate 25 is left unperforated so that it can form the rear wall of the heat exchanger. As shown in FIG. 4, plate 25 is formed with a flat central area 54; as shown in FIG. 2 this flat area 54 is of keyhole outline. Its periphery flares angularly as at 58 so as to merge with a second surrounding flat area 60. Area 60 in turn flares angularly at its marginal limits 62 for merger with the fiat peripheral flange 64. It will thus be seen that plate 25 is formed with three flat planar wall area 54, 60 and 64, said areas being offset from one another by the angular connecting wall areas 58 and 62.

Walls 21 through 24 are stamped to the same shape as wall 25 except that each of them is further formed with a keyhole-shaped opening 66 in its central area 54; the flat wall areas surrounding these openings 66 are welded together to form sealed connections between the plates. The various flanges 64 are also welded together to complete the sealed structure.

Wall 20 is similar to wall 25 except that it is formed with circular openings to accommodate the aforementioned collars 30, 46 and 48. The illustrated exchanger is formed of six plates but it will be appreciated that more or less numbers of plates may be employed, depending on the desired heat transfer capacity, wall temperatures, burner capacity, etc.

Openings 66 in the various heat exchanger plates provide the heat exchanger with a single central chamber of generally oblong or keyhole shape, as shown best in FIG. 2. This oblong passage communicates with the interior spaces defined by the aforementioned hollow fins 26, 27 and 28 comprised of the various wall areas 60 and 62. The drawings show wall areas 60 as flat areas; however they may be formed with transverse ridges or deformations at spaced points therealong to give a scrubbing action to the combustion, gases and treated air. Such ridges thus improve the heat transfer action. Additionally they strentghen the plates and alleviate stresses due to thermal effects.

COMBUSTION CHAMBER An important feature of the invention is the construction of the combustion chamber 14. As shown in FIG. 3,

the chamber is defined by a cylindrical metal reinforcing sleeve 68 and a snugly fitting liner 70 of refractory material such as fibrous alumina silica having kaolin or bentonite plasticizer. Such a fibrous refractory can withstand elevated temperatures, and can act as an insulator for the metal sleeve 68. However the fibrous material tends to flake or separate after prolonged exposure to flame; therefore use of a reinforcing metal sleeve 70 is suggested for prolonged service. Material technology advancements may in the future permit the elimination of the sleeve.

The refractory liner includes a rear wall 72 which is formed with an internal annular rib 74, the space 76 circumscribed by said rib being in the shape of a concave dish. As the flames from burner 12 strike wall area 76 they are caused to curl outwardly and back toward the burner as denoted by the arrows in FIG. 1. Some of the flames reach the inturned annular lip 78; at this point they may curl in as shown. The general concept of the combustion chamber design is to retain the flame within the chamber, but to guide it in a controlled swirling pattern for attainment of most complete combustion without having to feed in excess amounts of combustion air.

As the flame undergoes its swirling motion in chamber 14 it traverses the seven exhaust ports 16. These ports comprise a single port 16a in the chamber wall facing the aforementioned keyhole chamber, and six slot-like ports 16b in the chamber wall facing the various fin spaces 26, 27 and 28. Hot combustion gases issuing through ports 16!) fan out into the fin spaces for thus heating the various fin wall areas along their entire lengths (bottom to top in FIG. 2). Hot combustion gases issuing through port 16:: prevent inward collapse of the other gases issuing from ports 16b. Baflie 51 prevents a too direct flow of the port 16a gases toward flue 30 as would preclude most effective heat extraction.

The use of seven ports 16 as herein contemplated is advantageous in distributing the hot gases directly to the various fins 26, 27 and 28 so that each of the fins reaches approximately the same temperature. This is in contrast to certain prior art arrangements wherein the entire volume of hot gas issues through an open end of the combustion tube; in such arrangements the hot gases raise the temperature of certain parts of the heat exchanger without raising the temperature of other parts. Heat transfer to the treated air stream is promoted by uniform temperature differentials due to good and early distribution of the hot gases.

It will be noted that, with the exception of baflie 51, substantially all of the wall areas of the heat exchanger are primary heat transfer surfaces, i.e. walls having direct contact with hot gas on one side and treated air on the other side. This is in contrast to some heat exchangers which depend on auxiliary baffle walls to deflect the gases without acting as heat transfer surfaces. In the illustrated combustion chamber-heat exchanger arrangement the distribution of hot gases is accomplished with a minimum of bafliing.

COMBUSTION CHAMBER REMOVAL Periodically it is desirable to remove the combustion chamber, as for example when liner 70- is burned out or when soot deposits must be removed from the inner surfaces of the heat exchanger. In the illustrated arrangement liner 70 and sleeve 68 are removable as a unit. Removability may be achieved by forming a flange 80 on sleeve 68 and clamping the flange against the forward face of wall 44. This clamping function may be performed by the conventional plate 82 which mounts burner 12 on wall 44. Suitable screws or bolts (not shown) go through plate 82 into wall 44 to mount the burner; flange 80 is sandwiched against the rear face of plate 82 so that p ate 82 c amps the combustion chamber in place. Re-

moval of the burner and its mount plate 82 permits the sleeve 68-liner 70 assembly to be drawn out of the furnace for service purposes. The liner 70 is snugly but loosely retained within sleeve 68 so that the liner can be replaced without necessarily replacing the sleeve.

It will be seen that the various ports 16 are formed by registering holes in liner 70 and sleeve 68. There should be no rotation of the liner during service; otherwise the ports would partially or completely close. To prevent rotation of the liner a lug 84 may be provided on the liner so as to fit into a notch or slot 86 in sleeve 68. The reverse arrangement (a slot in the liner and a tab on the sleeve) could be used. Preferably the lug and slot should be such as to permit removal of the liner from the sleeve as previously described.

It will be appreciated that some variations in structure may be resorted to without departing from the invention as comprehended by the attached claims.

I claim:

1. A hot air furnace comprising a hollow heat exchanger designed to have the hot combustion gases flow along its interior surfaces, and the treated air flow along its exterior surfaces; said heat exchanger being a hollow oblong passage structure having parallel hollow fins extending laterally therefrom for its entire length; said heat exchanger having a first opening therein at one of its ends for reception of a burner, and a second opening at its other end for reception of a flue, whereby the combustion gases traverse the entire heat exchanger length, including the hollow fins; combustion chamber means comprising a refractory tube structure extending through the first opening into the heat exchanger; said tube structure being concentric with the burner means, and having an end wall arranged to deflect the flames in a back swirling pattern; said tube structure having ports therethrough registering with the hollow fins, whereby the hot combustion gases fan out into the fins as they emerge from the combustion chamber.

2. The furnace of claim 1 wherein the tube structure comprises a metallic reinforcing sleeve and a semifragile refractory liner snugly contained within said sleeve; the sleeve-liner assembly being slidable out of the heat exchanger for replacement purposes.

3. The furnace of claim 2 and further comprising a flat furnace partition coextensive in length with the heat exchanger; means for supporting the heat exchanger comprising a collar extending between the partition and the area of the heat exchanger which defines the first opening; the aforementioned burner being mounted on the partition, and the aforementioned sleeve having a flange which is sandwiched against the partition by the burner mounting, whereby removal of the burner permits withdrawal of the sleeve-liner assembly.

4. The furnace of claim 1 wherein the refractory tube structure is cylindrical, the aforementioned ports comprising two slots' for each hollow fin, each of said slots being elongated in the circumferential direction, each slot being oriented so that the gases issue therethrough crosswise of the longitudinal axis of the heat exchanger, whereby the gases reach into the hollow fins before they have travelled any substantial distance along the heat exchanger.

5. The furnace of claim 4 and further including an additional port in the tube structure, said additional port being oriented to discharge hot gases longitudinally into the oblong passage structure.

6. The furnace of claim 1 wherein the tube structure end wall is formed with an internal annular rib, which defines a concave dish-like wall area causing flame components from the burner to curl outwardly and then backwardly toward the burner.

7. The furnace of claim 6 wherein the tube structure is formed with an inturned annular lip in surrounding relation to the burner, said lip serving to deflect some 5 6 of the aforementioned backwardly travelling flame com- References Cited ponents toward the combustion chamber axis.

8. The furnace of claim 1 wherein the tube structure UNITED STATES PATENTS comprises a metallic reinforcing sleeve and a semi-fragile 21591440 5/1939 Llvar 126-110 refractory liner snugly contained within said sleeve; 2,501,041 3/1950 Gates 126116 the sleeve-liner assembly being slidable out of the heat 5 215611100 7/ 1951 Dahlstrom 126-110X exchanger for replacement purposes; said sleeve and 3,382,862 5/1968 Martz 126115 X liner being cylindrical, and being separable from one CHARLES J MYHRE Primary Examiner another; said sleeve and liner having interfitting slot-lug means thereon for preventing the liner from rotating dur- 10 U.S. Cl. X.R.

ing service. 126ll6; 431--1 15 

